Technical Field
The present disclosure generally relates to imaging systems which read symbols, such as text and machine-readable symbols.
Description of the Related Art
Imaging systems that perform measurement, inspection, alignment of objects and or decoding of symbols (e.g., machine readable symbols, text) are used in a wide range of applications and industries. These systems utilize one or more image sensors which acquire images of an object, and process these acquired images using a suitable processor-based imaging system to perform one or more imaging system processes to generate the desired output based upon the image's processed information. This image information is generally provided as an array of image pixels each having various colors and/or intensities. In the example of a machine-readable symbol reader, the user or an automated process acquires images of an object that is believed to contain one or more machine-readable symbols (e.g., barcodes symbols). One or more images may be processed to identify machine-readable symbol features, which are then decoded by a decoding process to obtain information represented by the machine-readable symbol. A similar process may be used to identify alphanumeric data (e.g., letters, numbers), which process may be referred to as optical character recognition (OCR).
One use for machine-readable symbol readers, also referred to herein as imaging systems or imagers, is to track objects moving along a line (e.g., a conveyor belt) in manufacturing and logistics environments. In such applications, the imaging system may be positioned above or on one or more sides of the line at an appropriate viewing angle to acquire any expected machine-readable symbols on respective objects as they move through a field of view of the imaging system. The focal distance of the imaging system with respect to an object may vary depending on the placement of the imaging system with respect to the line and the size of the object. That is, a larger object may cause machine readable symbols thereon to be located closer to the imaging system, while smaller/flatter objects may contain machine-readable symbols that are further from the imaging system. In each case, the machine-readable symbol should appear with sufficient resolution to be properly imaged and decoded. Therefore, the field of view of a single camera of an imaging system, particularly in the widthwise or lateral direction (perpendicular to line motion), may be limited. If an object and/or the conveyor line are relatively wide, the lens and sensor of a single imaging system may not have a sufficient field of view in the lateral direction to cover the entire width of the line while maintaining the needed resolution for accurate imaging and decoding of machine-readable symbols. Failure to image the full width of a line may cause the imaging system to miss machine-readable symbols that are outside of the field of view.
There are at least a few techniques that may be employed to overcome the limitation in field-of-view of a single imaging system. For example, one can employ multiple imaging systems focused side-by-side to fully cover the width of a conveyor line. Alternatively, a line-scan system with inherently wider field of view may be employed. Yet another example is to employ a larger sensor in a single imaging system to provide the desired resolution for imaging the scene along the widthwise direction. However, several of these solutions are undesirable due to increased cost, hardware, optics, and/or complexity.